It is where I find the pv tool extremely nice.
To install it under gentoo :
emerge -a sys-apps/pv
Example of a disk imaging session (all as root):
First make sure the targeted hard drive here /dev/sdb will be accessed read-only (for those still without a physical write blocker :P ):
losetup /dev/loop0 -r /dev/sdb
pv acts by default somewhat like cat :
pv /dev/loop0 | tee image.dd | md5sum 10.8GB 0:01:24 [ 133MB/s] [==> ] 4% ETA 0:28:55At the end of the process it gives you nicely your md5sum: